a) Field of the Invention
The present invention relates to a brushless motor having a stator core and, more particularly, to a brushless motor in which the balance between the driving magnet and the stator core in terms of the magnetic attraction force is improved.
b) Background Art
A brushless motor having a structure shown in FIG. 8 is known as a conventional peripherally opposed type brushless motor having a stator core. Referring to FIG. 8, a stator core 48 having a number of radially extending salient poles is fixed onto a substrate 10. Each salient pole has a salient-pole umbrella portion 49 at its tip end, each salient pole being wound therearound with a driving coil 50. The driving coils 50 have a three-phrase structure. The stator core 48 of the illustrated example originally has twenty four salient poles, three of which are, however, removed on an every-other basis. Between two adjacent salient-pole umbrella portions 49 having one removed salient pole therebetween, there are formed open slots B1, B2, and B3; the dimension or width of each of which is larger than the gap between the salient-pole umbrella portions 49 which are originally provided. Magnetic sensors H1, H2, and H3, each consisting of a Hall element and the like, are disposed in the open slots B1, B2, and B3, respectively.
A flat-cup shaped rotor, not shown, is rotatably supported so as to cover the stator core 48 from above the same. On an inner peripheral surface of this rotor, a driving magnet is integrally mounted, and the salient-pole umbrella portions 49 are disposed opposing the driving magnet so that tip end faces thereof may be located with respect to an inner peripheral surface of the driving magnet at a suitable interval therebetween. As is well known, the above-mentioned three magnetic sensors H1, H2 and H3 detect the magnetic poles of the driving magnet and switch the energization of the driving coils 50 of which they are in charge, thereby driving the rotor to rotate.